This invention relates to artificial light detectors. More particularly, this invention relates to portable, handheld artificial light detectors that can distinguish artificial light from sunlight and low-frequency artificial light from high-frequency artificial light.
As used herein, artificial light is modulated light such as from a lamp powered by an AC source. Examples of such lamps include incandescent, fluorescent, and high intensity discharge lamps. As also used herein, “luminaire” refers to a lighting fixture that outputs modulated light or that has one or more lamps powered by an AC source. “Artificial light” does not include light from a device powered by a DC source, such as, for example, a battery-operated flashlight or typical automobile headlight.
Sunlight refers to light from the sun and may also be referred to as natural light, daylight, and outside light.
Light detectors are known and typically include a photocell circuit or device that responds either when there is a sudden change in light level or when there is an absolute light level change. In addition to turning lamps on and off in response to the amount of ambient sunlight detected in a monitored area, light detectors can also be used to track the amount of time that luminaires are on in a monitored area. This information can be used to determine energy costs associated with those luminaires. Such costs can be significant in large office, warehouse, and retail areas. However, many known light detectors cannot distinguish artificial light from sunlight. Thus, these known light detectors cannot be used to determine energy costs in areas that receive sunlight, because they cannot accurately indicate whether or not the luminaires in those areas are on or off during daylight hours.
Furthermore, few, if any, known light detectors can identify types of artificial light. Different types of artificial light have different energy costs. For example, artificial light from a low-frequency source (e.g., an incandescent bulb or fluorescent lamp powered by a magnetic ballast) generally has higher energy costs than artificial light from a high-frequency source (e.g., a fluorescent lamp powered by an electronic ballast). Thus, light detectors capable of identifying types of artificial light could be used to identify luminaires whose replacement may lower energy costs.
Lastly, light detectors that can distinguish artificial light from sunlight and identify types of artificial light would be even more advantageous if they were portable and could be handheld. An auditor can then quickly and easily survey an area without having to access and inspect each luminaire or group of luminaires in order to determine what type of artificial light is generated.
In view of the foregoing, it would be desirable to be able to provide a light detector that can distinguish artificial light from sunlight.
It would also be desirable to be able to provide a light detector that can identify types of artificial light.
It would further be desirable to be able to provide a portable, handheld light detector that can distinguish artificial light from sunlight and identify types of artificial light.